1. Field of the Invention
The object of the invention is fluidizing apparatus comprising a built-in heat exchanger adapted to exchange heat with the fluidized bed.
2. Description of the Prior Art
Generally speaking, such heat exchange is in the direction to remove heat energy from the fluidized bed, especially when the latter is produced in a furnace designed to burn fluidized coal. Obtaining combustion in a fluidized bed is dependent on control of the temperature within the bed.
It is known to place heat exchanger tubes within a fluidized bed. Their heat exchange coefficient is varied by placing them in an area where the level of the bed may be varied and by arranging things so that the bed is at different levels, which is achieved by appropriate variation in the velocity of the fluidizing gas. By modifying the depth of the fluidized bed, the exchanger tubes are immersed in it to varying degrees. The exchange coefficient is much higher within the bed (300 W/m.sup.2 /.degree.C., for example) than outside the bed (20 W/m.sup.2 /.degree.C., for example). Significant variation in the level of the bed, in particular through modifying the flowrate of the fluidizing gas, introduces difficulties and in particular results in a significant variation of the head loss by the fluidizing gas distribution grid, whence the risk of inadequate fluidization of the charge.